Are there penalties for invading those kinds of homes in the UK? Where I used to live (a city of ~100K in Israel) there are probably 500-1000 properties on and around the marina owned by foreign nationals that are conspicuously empty for 9 months of the year, I considered squatting in one of those but if I'm discovered I'd be liable for the something like 3 times the rent for the period I lived there.

Presumably if the penalty for squatting unattended apartments were lower, the owners might be more motivated to find occupants.